In recent years, there is a strong desire for an increase in the size of television sets and display devices for displaying information. Representative examples of large-sized display devices are display devices in which self-light-emitting elements such as light-emitting diodes (LEDs) are arranged in a matrix array and projection display devices; however, these have disadvantages in terms of image quality. Therefore, a further increase in the size of direct-viewing type liquid crystal display devices (LCDs) and plasma display devices (PDPs), which are capable of displaying with a high image quality, is being desired.
Since a direct-viewing type liquid crystal display device or a plasma display device is basically formed on a glass substrate, its screen size depends on the substrate size. Currently, the largest of glass substrates (mother substrates) that are used for the production of liquid crystal display devices are those of the eighth generation (2200 mm×2400 mm), and liquid crystal display devices whose diagonal is about 100 inches are being produced by using these substrates. The substrates that are available for mass production will become more increased in size, however at a slow rate. It is difficult to immediately provide display devices with the larger areas that are required on the current market.
Therefore, as a method of realizing a large-screen display device, there has been a conventional attempt of realizing a make-believe large-screen display device by arraying a plurality of display devices (which may be referred to as tiling). However, the tiling technique induces a problem of visible joints between the plurality of display devices. This problem will be described by taking a liquid crystal display device for example.
Note that a liquid crystal display device mainly includes a liquid crystal display panel, a backlight device, circuits for supplying various electrical signals to the liquid crystal display device, and a power supply, as well as a housing in which to accommodate these. The liquid crystal display panel is mainly composed of a pair of glass substrates and a liquid crystal layer retained therebetween. On one of the glass substrates, a color filter layer and a counter electrode are formed, while on the other glass substrate, TFTs, bus lines, a driving circuit for supplying signals to them, and the like are formed. The screen size of a direct-viewing type liquid crystal display device is determined by the screen size of its liquid crystal display panel. Moreover, the liquid crystal display panel has a display region composed of a plurality of pixels, and a frame region surrounding it. In the frame region, a sealing portion for attaching together the pair of substrates and also sealing and retaining the liquid crystal layer, an implementation of driving circuitry for driving the pixels, and the like are formed.
Thus, since the frame region not contributing to any displaying exists in a liquid crystal display panel, when a large screen is constructed by arraying a plurality of liquid crystal display panels, the image will have joints. This problem is not limited to liquid crystal display devices, but is shared among direct-viewing type display devices, e.g., PDPs, organic EL display devices, and electrophoresis display devices.
The Applicants disclosed on Jun. 7, 2010 a multi display system in which a plurality of 60V-type liquid crystal display panels were deployed in matrix tiling, with a width (also referred to as a “system frame width”) of 6.5 mm existing between adjacent display regions (where each single display panel had a frame region which was 2.4 mm wide in the right side and the lower side and 4.1 mm wide in the left side and the upper side) (http://www.sharp.co.jp/corporate/news/100607-a.html). This multi display system has the smallest system frame width ever, and its joints are not too conspicuous. However, there is a desire for developing a display device with further obscured joints.
Patent Document 1 discloses a display device which realizes jointless displaying by further providing a display panel at the rear face of two or more display panels.
Non-Patent Document 1 describes that it is possible to obscure joints by allowing a noise component to be contained in signals for displaying in the display region near joints.